Apparatus for painting the inner surface of pipes

ABSTRACT

A method and apparatus for interior painting of a pipe, particularly of small diameter, is characterized by filling of a pipe with both ends open with paint, hanging the pipe vertical and passing a ball of a diameter smaller than the inside diameter of the pipe from the upper end of the pipe to fall down by its gravity through the pipe and strip off excessive paint so as to form a film of uniform thickness of paint of the inner surface of the pipe.

United States Patent Kasano et al.

[54] APPARATUS FOR PAINTING Tn]:

INNER SURFACE OF PIPES [72] Inventors: Kimiaki Kasano, Amagasaki; IchiroKaya, Sakai, both of Japan {73] Assignee: Kansai Paint Company Limited,

' I-Iyogo-ken, Japan [22] Filed: Nov. 3, 1971 [21] Appl. No.: 195,510

Related US. Application Data [62] Division of Ser. No. 835,705, June 23,1969, Pat, No.

[30] Foreign Application Priority Data July 2, 1968 Japan .Q -4.43/46399[52] US. Cl ..ll8/l05, 118/408, ll8/DIG. 10 [51] Int. Cl. ..B05c 7/00,B05c 11/02 [58] Field of Search...1 18/408, DIG. 10, 105; 117/97 [5 6] 7References Cited UNITED STATES PATENTS 2,100,587 11/1937 Chalker..lI8/l05 [451 Dec. 12,1972

2,449,783 9/1948 Laidig et al ..l l8/408 X 2,950,702 8/1960 Ferguson etal. ,.1 18/408 OTHER PUBLICATIONS German Printed application,Auslegeschrift,

1,149,421, May 30, 1963.

Primary Examiner-John P. McIntosh Attorney--Larson and Taylor [5 7]ABSTRACT A method and apparatus for interior painting of a pipe,particularly of small diameter, is characterized by filling of a pipewith both ends open withpaint, hanging the pipe vertical and passing aball of a diametersmaller than the inside diameter of the pipe from theupper end of the pipe to fall down by its gravity through the pipe andstrip off excessive paint so as to form a film of uniform thickness ofpaint of the inner surface of the pipe.

1 Claim, 4 Drawing Figures PATENTED DEC 12 m2 sum 1 or 2 PATENTEU Z3.705.569

sum 2 [1F 2 APPARATUS FOR PAINTING THE INNER SURFACE OF PIPES Thisapplication is a division of application Ser. No. 835,705 filed June 23,1969, now US. Pat. No. 3,657,000.

This invention relates to an apparatus for painting the inner surface ofa pipe and is aimed at providing pipe particularly of small diameterwith inner surface evenly painted.

In the conventional methods uniform coating of the inner surface of apipe extremely large inside diameter could be performed by means ofspraying, but with long pipe of smaller inside diameter, such as lessthan 53 mm inside diameter, uniform coat of the inner surface could notbe obtained. And, for example, when a pipe of smaller diameter is firstfilled with paint, and then the pipe is hung vertical to let paint inexcess flow down, there inevitably results difference in the thicknessof coat between at lower and upper ends, failing to provide uniformthickness of the coat, and is accompanied by sagging and furthermore ittakes longer time in coating work. No such sprayer is known in the art,being capable of painting the inner surface of a pipe .of less than 53mm inside diameter. Also high viscosity paint can not be used in spraypainting for this purpose.

The object of the invention is to provide an apparatus for forminguniform coat of paint by a simple operation by using a relatively highviscosity paint in painting the inner surface of a pipe, particularly ofsmall diameter. According to the invention, in forming a film of uniformthickness on the inner surface of a pipe with open ends, the pipe isfirst filled with paint, and then hung vertical, and preferably, afterthe paint has partly flowed down, then a ball having diameter slightlysmaller than the inside diameter of the tubular body is inserted throughthe upper end of the pipe to fall down through the hollow, wherebyuniform film is formed on the inner surface of the pipe. Thus, accordingto the invention uniform film of paint as desired is formed, by firstfilling the hollow portion of a pipe with both ends open with paint,hanging the pipe substantially vertical, preferably, after letting thepaint within fall down to some extent, and then passing a ball of adiameter allowing a clearance necessary for producing required thicknessof film, from upper end of the pipe to fall down by its gravity, so asto strip off excessive aint. p The invention will be hereinafterexplained according to the attached, drawings, in which.

FIG. 1 is a side elevation with a partial longitudinal section of apreferred embodiment of the invention.

FIG. 2 is an enlarged longitudinal section of part of FIG. 1.

FIG. 3 is a sectional view along A-A line of FIG. 2, and

FIG. 4 is an enlarged-sectional view along B--B line of FIG. 1.

In FIG. 1, pipe 1 is suspended from tact-conveyor 3 by hanger 2, saidtact conveyor moving intermittently at regular intervals in thedirection of arrow head. When pipe I hung on tact conveyor 3 reachespaint inlet 5 by movement of tact conveyor 3, tact conveyor stops, paintinlet 5 moves upward actuated by arm operator 6 held by stay 21, to fitthe lower opening of pipe 1. Then coating composition in tank 8 ispumped into pipe 1 by pump 7 through hose 19 and hollow arm 4. When pipeI is filled to the upper extremity, paint inlet 5 and hollow arm 4 arelowered by arm operator 6, and tact conveyor again moves in thedirection of arrow head.

On the other hand, the ball is supplied to pipe 1 in the followingmanner during operation. Number of balls are kept in box 20 provided onthe upper part of tact conveyor 3, and when pipe filled with paint atthe upper end or its vicinity as above reaches bel ow ball outlet 23 ofbox 20, shutter 22 at the outlet 23 of box 20 opens and a ball islowered to the upper opening of pipe 1 below the outlet 23. When shutter22 is opened shutter 25 provided in ball feed pipe 24 in a distance fromshutter 22 of slightly larger than the diameter of ball 13 is shut tolet only one ball drop from ball exit 23. When ball 13 has droppedshutter 22 is shut whereby another ball is delivered into pipe 24. Allthe above supply of paint into pipe and the supply of ball 13 arecarried out automatically by means of a regulator.

The above operation takes place in a given length of time, and conveyor3 is driven again by means of time switch. The supply of the balls mayalso be done manually. Ball 13 in pipe 1 falls by gravity within thepipe whileconveyor 3 is moving, forcing down paint 16 to producerequired thickness of film 18. Hanger 2 provided on conveyor 3 isequipped with at least a pair of catches 27 having teeth 26 at the end,facing diagonally and movable up and down, and between these opposingcatches 27 pipe 1 is inserted and by slightly lowering pipe 1 teeth 26of catches 27 engage with outside surface of pipe 1 to be suspended.Balls falling through pipe 1 are collected in ball receptacle 15, andare washed for reuse in a separate tank with an organic solvent whichdissolves the paint. Excessive paint 16 which is stripped off from pipe1 is delivered to paint tank 8 for recirculation. Pipes 1 on which filmof paint is formed further move successively and are baked as requiredby baking oven 17 to obtain final products. In this way of painting, thecoated film is sufficiently thin according to the viscosity of paintused after the ball is passed through and no sagging is liable to occur.The manner of the ball passing through pipe 1 is shown in FIG. 2 and 3,in enlarged drawings. In FIG. 2 and 3, the paint filling the pipe 1 isstripped off by ball 13 to result in desired thickness of coat. In theinvention, the method of filling pipe 1 with paint is not limited tofilling from the lower end, and it can be done, for example, by pluggingthe bottom end of pipe 1 and charging it from upper end and removing theplug for further operation.

When the ball is inserted from the upper end of pipe 1 it is inevitablethat the ball is somewhat shaken in the direction of the diameter of theball for a length of about 10-20 mm from the upper end, but after thatthe ball will fall straight through the center of pipe 1. Accordingly,either by cutting off such length of 10-20 mm from the end or bytemporarily joining a separate pipe of same inside diameter to the upperend of pipe 1 for coating and removing it after coating, uniformthickness of the coat can be obtained throughout.

The preferred embodiment of the present invention is advantageous inthat after filling pipe 1 with paint, the paint is allowed to partlyfall down (see drawings) to let the ball fall through the center of piperapidly, whereby the thickness of film within is unified.

The paints to be used in the invention may vary, but generally tar-epoxyresin-based paints of viscosity of about 60-130 KU (Krebs Unit),polyvinyl chloride solbased paints of about 80-110 KU, epoxy resin-basedpaints of about 60-130 KU and polyurethane resinbased paints of about60-90 KU, etc. are used. These paints are selected by considering theinside diameter of pipe to be painted, thickness of film to be formed,specific gravity of balls used, etc. As the balls to be used aredesirable those of a material having specific gravity of about 1.0-8.0.Steel balls (specific gravity of about 7.8), Porcelain balls (generallyspecific gravity of about 3.5), plastics balls (generally specificgravity of about 1.0-2.0), stainless steel balls (generally specificgravity of about 7.8), glass balls (generally specific gravity about of2.2-6.3), etc. can be effectively used. The diameter of these balls isselected in consideration of inside diameter of pipe and clearance fromsaid inside diameter of pipe, necessary to produce film of paint to thedesired thickness. The clearance generally is about 1.3-2 times thedesired thickness of film depending on the concentration of paint, forexample, the clearance of about 140-220 p. is desirable to obtain a film100 p. thick. The specific gravity of the balls can be selected freelyaccording to the viscosity of paint and the diameter of pipe. The methodof the invention can be most advantageously applied to the painting ofsteel pipe of 12.7 52.9 mm inside diameter. The pipe, ball and paint invarious combinations according to the method of the invention areexemplified in Table 1 below.

In the method of operation it is also possible to introduce relativelypressurized air into pipe after inserting the ball from the upperopening of pipe to facilitate the fall of the ball through pipe.

The apparatus of the invention can be said to have an extremely highindustrial value in that the interior surface of a pipe of smallerdiameter is painted to uniform and desired thickness by a simpleoperation.

Concrete explanation of the method of the invention is done by examplesto follow.

EXAMPLE 1 By the equipment as shown in FIG. 1 interior coating wascarried out under the following conditions:

TABLEZ Inside diameter 27.6 mm (A SGP) Pipe Length 5.5 m

Material Steel Diameter 27.0 mm Ball Weight 80 g Material Steel TypePolyvinyl chloride Paint sol-based enamel (1. .5900 V. 9 K11- m.--

Clearance between pipe and 0.3 mm ball I Operation Falling veconditionslocity of ball 30 sec/5.5 n1

Distance between p p i9 1 1 Speed of tact Stop 35 sec. and conveyoradvance 5 sec.

Drying conditions 190 10CX10 min.

No sagging was observed in the film immediately after coating and after30 minutes, and uniform film of 2101-15 p. was obtained. The upper endof the pipe was cut ofi' by 10 mm. When transporting the pipes aftercoating, the coated pipes were taken down from the hanger of tactconveyor, laid horizontally for baking without any sagging beingobserved.

EXAMPLE 2 By the equipment of FIG. 1 was conducted interior paintingunder the following conditions.

TABLE 3 Inside diameter 12.7 mm 52.9 mm (10A 561) (50A 861) Pipe Length5.5 rn 5.5 m Material Steel Steel Diameter 12.2 mm 52.0 mm Ball Weight7.4 g 260 g Material Steel Porcelain Viscosity 60 RU KU Paint TypeEpoxy-resin Tar-epoxy based enamel resin-based enamel Clearance 0.25 mm0.45 mm Falling ve- 43-50 sec/5.5 in 15-18 sec/5.5 m Operlocity of ballation con- Distance be- 50 mm 50 mm ditions tween pipes Speed of tactStop 60 sec Stop 20 sec conveyor Advance 5 sec. Advance 5 sec Dryingconditions CX15 min. 20Cfix24 hr.

- By coating under the above conditions A and B, the thickness ofobtained film was 110:20 p. for A and 300135 p. for B, and thethicknesses were substantially uniform throughout, exhibiting no notabledifferences between upper and lower parts, and even after 30 minutesvertical suspension of the pipes no sagging was observed.

What we claim are:

1. An apparatus for painting the inner surface of a pipe, comprising aconveyor having hangers attached in a longitudinal row at fixedintervals, by which pipes are suspended detachably, said conveyor movinginterrnittently for a distance between pipes; paint-feeding cup meanswhich moves up and down in unison with the intermittent movement of saidconveyor, rises and engages with the lower opening of the pipe to becoated, suspended from the hanger when the conveyor stops, and lowersdisengaging from said pipe opening when the conveyor is moving; means toso raise and lower said cup; pump means with its suction port connectedto paint tank means and discharge port means connected to said cup,which supplies paint into the pipe through said cup to the height nearthe upper end of the pipe when said cup is engaged with the loweropening of the pipe; ball holder means located adjacent said

1. An apparatus for painting the inner surface of a pipe, comprising aconveyor having hangers attached in a longitudinal row at fixedintervals, by which pipes are suspended detachably, said conveyor movingintermittently for a distance between pipes; paint-feeding cup meanswhich moves up and down in unison with the intermittent movement of saidconveyor, rises and engages with the lower opening of the pipe to becoated, suspended from the hanger when the conveyor stops, and lowersdisengaging from said pipe opening when the conveyor is moving; means toso raise and lower said cup; pump means with its suction port connectedto paint tank means and discharge port means connected to said cup,which supplies paint into the pipe through said cup to the height nearthe upper end of the pipe when said cup is engaged with the loweropening of the pipe; ball holder means located adjacent said conveyor atthe upper end of said pipe and containing a number of balls which falldown through the interior of the pipe so as to strip out the paintwithin to produce a film of uniform thickness; ball feeder means whichdrops one ball through the upper opening of the pipe each time the pipefilled with paint stops below said ball outlet and paint receptaclemeans to receive the paint thus driven down through the pipe.